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Synchronous Digital Hierarchy (SDH

)
• Agenda
Introduction Quality standards
SDH advantages
Bit Rates
Standard Frame representation
Frame structure
Transport overhead
SDH Multiplexing
Concatenation
Justification
Architecture
SDH Equipment
Network topologies
Network protection
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Synchronous Digital Hierarchy (SDH)
• Introduction
SONET(Synchronous Optical Network) or SDH(Synchronous Digital
Hierarchy) as it's known in Europe, is a set of standards for interfacing
Operating Telephone Company(OTC) optical networks.

They are a set of global standards for interfacing equipment from different
vendors(One of the few where telephony is concerned).

SONET is the protocol for North America and Japan while SDH is the
definition for Europe. The differences between SONET and SDH are
slight.

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Synchronous Digital Hierarchy (SDH)
• SDH Advantages versus PDH

PDH principle

E1 E2 E2 E1

E3 E3

Channel n°7 E4 Channel n°7

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Synchronous Digital Hierarchy (SDH)
• SDH Advantages versus PDH

SDH principle

SDH Add/Drop SDH
channels Equipment multiplexer Equipment

Channel n°X Channel n°Y

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Synchronous Digital Hierarchy (SDH)
• SDH Advantages versus PDH
SDH is based on the principal of direct
synchronous multiplexing.

Essentially, separate, slower signals can be
multiplexed directly onto higher speed SDH signals
without intermediate stages of multiplexing.

SDH is more flexible than PDH and provides
advanced network management and maintenance
features.
Can be used in the three traditional telecommunications
areas: long-haul networks, local networks and loop
carriers. It can also be used to carry CATV video traffic.

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160 STM-8 OC-36 STS-36 1866. Bit Rates Optical Electrical Line Rate SDH Level Level (Mbps) Equivale nt OC-1 STS-1 51.080 STM-4 OC-18 STS-18 933.84 --- OC-3 STS-3 155.520 STM-1 OC-9 STS-9 466.120 STM-6 OC-24 STS-24 1244.240 STM-13 OC-48 STS-48 2488.320 STM-16 OC-96 STS-92 4976.640 STM-32 6 OC-192 STS-192 9953.280 STM-64 .56 STM-3 OC-12 STS-12 622.

488 Gbit/s STM16 9.Synchronous Digital Hierarchy (SDH) • Bit Rates International organization defined standardized bit rates : 155. 520 Mbit/s STM1 622.953 Gbit/s STM64 7 . 080 Mbit/s STM4 2.

8 .Synchronous Digital Hierarchy (SDH) • SDH : Standard Frame Representation 0 1 1 0 0 1 1 0 0 1 0 1 1 0 1 0 1 0 Bit Transmission Byte Transmission Standard Frame Representation The Standard STM1 Frame is 9 Rows x 270 Columns and is completely transmitted in 125 µs.

the standard SDH frame representation is a : MATRIX with 9 rows How to read the matrix 1 9 9 .Synchronous Digital Hierarchy (SDH) • SDH : Standard Frame Representation Everywhere in the world.

08 Mbps Overhead 36 Col 1.176 Col 10 .52 Mbps 9 Col 261 Col 9 Rows Section STM4 622.32 Mbps Overhead 144 Col 4. Synchronous Digital Hierarchy (SDH) • SDH frame structure Each Frame is STM1 Sent in 125µs! 9 Rows Section Overhead 155.044 Col 9 Rows Section STM16 2488.

Synchronous Digital Hierarchy (SDH) • SDH frame structure All SDH frames have the same structure : Section OverHead SOH Payload (data) Regenerator Section Overhead (RSOH) Pointer Multiplexing Section Overhead (MSOH) 11 .

Synchronous Digital Hierarchy (SDH) • Transport Overhead : SOH R SOH (Payload) A1 A1 A1 Pointer A2 A2 A2 J0 B1 E1 F1 STM1 D1 D2 D3 frame M SOH AU4 pointer AU4 Pointer B2 B2 B2 K1 K2 D4 D5 D6 D7 D8 D9 D10 D11 D12 S1 M1 E2 12 .

13 .Synchronous Digital Hierarchy (SDH) • Transport Overhead : SOH A1 and A2 : frame alignment word A1 A1 A1 A2 A2 A2 J0 B1 : Regenerator setion error B1 E1 F1 monitoring D1 D2 D3 J0 : STM1 identifier (16 bytes word) B2 B2 B2 K1 K2 E1 : Service channel (transport a 64 D4 D5 D6 Kbit/s channel) D7 D8 D9 F1 : user channel. May be used for D10 D11 D12 network exploitation S1 M1 E2 D1-D3 : Data communication Channel at 192 Kbit/s.

Synchronous Digital Hierarchy (SDH) • Transport Overhead : SOH B2 : Multiplexing section error A1 A1 A1 A2 A2 A2 J0 monitoring B1 E1 F1 K1 and K2 : Automatic protection D1 D2 D3 switching signalling B2 B2 B2 K1 K2 D4-D12 : Data communication D4 D5 D6 Channel at 576 Kbit/s. D7 D8 D9 S1 : bytes of synchronization status D10 D11 D12 M1 : Binary code for number of S1 M1 E2 errored blocks E2 : service channel at 64 Kbit/s 14 .

Synchronous Digital Hierarchy (SDH) • Transport Overhead : AU 4 pointer A1 A1 A1 A2 A2 A2 J0 The secret to making SDH work is the B1 E1 F1 payload pointer. the SDH D10 D11 D12 multiplexer finds the beginning of a frame for each tributary. They are not necessarily B2 B2 B2 K1 K2 aligned with each other or with the clock in the multiplexer. S1 M1 E2 15 . To resolve this D4 D5 D6 problem. remember that this is a D7 D8 D9 SYNCHRONOUS network. The tributaries D1 D2 D3 coming into a multiplexer may have been created with a clock running at a different speed.

have a look on the following picture : The container can move inside 155 Mbit/s the wagon STM 1 16 .Synchronous Digital Hierarchy (SDH) • Transport Overhead : AU4 pointer In order to illustrate the pointer working.

Synchronous Digital Hierarchy (SDH) • Transport Overhead : AU4 pointer You have exactly the same phenomenon in SDH : Beginning of VC4 17 .

It has mechanisms for dealing with tributaries that are not running at the same clock rate.Synchronous Digital Hierarchy (SDH) • SDH Multiplexing SDH is a new way of multiplexing slow signals onto a faster signal. 140 Mbit/s E4 150 Mbit/s E4 E4 VC4 VC4 155 Mbit/s STM 1 STM 1 STM 1 18 .

Synchronous Digital Hierarchy (SDH) • SDH Multiplexing Translation of the previous picture in SDH language : STM1 frame R SOH Payload M SOH VC4 P O E4 H 19 .

Synchronous Digital Hierarchy (SDH) • SDH Multiplexing STM4 frame R SOH Payload M SOH VC4 VC4 VC4 VC4 P P P P O O O O H E4 H E4 H E4 H E4 20 .

Synchronous Digital Hierarchy (SDH) • SDH Multiplexing : another example (E3=>STM1) You can map 3 E3 (34 Mbit/s) onto one STM1. VC3 = TU-3 VC3 = TU-3 VC3 = TU-3 P P P O E3 (A) O E3 (B) O E3 (C) H H H S S P P P P T T O O O O U U H H H H F F F F 21 .

Synchronous Digital Hierarchy (SDH) • SDH Multiplexing : another example (E3=>STM1) STM1 frame R SOH Payload M SOH VC4 P O H 22 .

Synchronous Digital Hierarchy (SDH) • The SDH Multiplexing map xN E4 C4 VC4 AU4 STM-N (140 Mbit/s) x3 E3 x1 C3 VC3 TU3 TUG-3 (34Mbit/s) x7 TUG-2 E1 C12 VC12 TU12 x3 (2Mbit/s) 23 .

Synchronous Digital Hierarchy (SDH) • What is the « concatenation » ? STM4 frame R SOH Payload M SOH VC4 VC4 VC4 VC4 Concatenated VC4 (VC4-4c) 24 .

Synchronous Digital Hierarchy (SDH) • What are the different « concatenation » possibilities? STM1 1 standard VC4.No concatenation ! SOH VC4 25 .

Synchronous Digital Hierarchy (SDH) • What are the different « concatenation » possibilities? STM4 4 standard VC4 1 concatenated VC4-4c SOH VC4 VC4 VC4 VC4 SOH VC4-4c 26 .

Synchronous Digital Hierarchy (SDH) • What are the different « concatenation » possibilities? STM16 16 standard VC4 4 concatenated VC4-4c 1 concatenated VC4-16c VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4 VC4-4c VC4-4c VC4-4c VC4-4c VC4-16 27 .

Synchronous Digital Hierarchy (SDH) • What are the different « concatenation » possibilities? STM64 64 standard VC4 16 concatenated VC4-4c 4 concatenated VC4-16c 1 concatenated VC4-64c 28 .

Synchronous Digital Hierarchy (SDH) • What is the « Justification » ? In theorie. But in pratical. the E4 speed should E4 C4 be the same than the C4 speed. 29 . you need a special system called « justification » each time you want to map a tributary. If you want to adapt the speed variation. the E4 speed can be a little bit faster or slower than the theorical speed.

Synchronous Digital Hierarchy (SDH) • What is the « Justification » ? J J U U E4 C4 S S T T J Positive U S justification T When the J J J U U U tributary is slower E4 C4 S S S T T T 30 .

Synchronous Digital Hierarchy (SDH) • What is the « Justification » ? J J U U E4 C4 S S T T J Negative U S justification T When the J J U U tributary is faster E4 C4 S S T T 31 .

Synchronous Digital Hierarchy (SDH) • SDH architecture basics Terminating equipment Repeaters STM1/4/16/64 Regenerator section Multiplexing section VC4 high path 32 .

33 . B1 errored blocks . Each repeater monitors defects such as Loss Of Signal...Synchronous Digital Hierarchy (SDH) • SDH architecture basics : Regenerator section Terminating equipment Repeaters STM1/4/16/64 Regenerator section is the basic segment of SDH network. It is the smallest entity which can managed by the system. the R-SOH is fully recalculated. Loss Of Frame. By passing through a repeater.

Detects defects and errored blocks and generated special alarm in the forward and backward direction. Manage the Automatic Protection Switching wtih K1 and K2 bytes.Synchronous Digital Hierarchy (SDH) • SDH architecture basics : Multiplexing section Terminating equipment Repeaters STM1/4/16/64 The multiplexing section is the entity delimitated by 2 equipment which process the payload of an STM-N. Regenerated a complete SOH. 34 .

Synchronous Digital Hierarchy (SDH) • SDH architecture basics : VC4 high path Terminating equipment Repeaters STM1/4/16/64 The VC4 High Path is an entity which transport a C4 container from end to another end of a network. 35 . A VC4 can be affected to one customer.

Synchronous Digital Hierarchy (SDH) • SDH equipments : Terminal Multiplexer » Input: Low Bit Rate and PDH/T-Carrier Tributaries » Output: High Bit Rate SDH Signals 6701 3'+ 7&DUULHU 36 .

Etc. Dispersion. 6701 6701 37 .Synchronous Digital Hierarchy (SDH) • SDH equipments : Regenerator » Input: STM-N Synchronous Signal » Output: STM-N Synchronous Signal » Reconditions Transmission To Minimize Jitter.

Synchronous Digital Hierarchy (SDH) • SDH equipments : Transponder (λ Converter) » Input: STM-N Synchronous Signal at λ1 » Output: STM-N Synchronous Signal at λ2 » Changes the Wavelength of the Transmission Signal 6701 6701 λ1 λ2 38 .

Synchronous Digital Hierarchy (SDH) • SDH equipments : Add/Drop Multiplexer » Input: STM-N Synchronous Signal » Output: STM-N Synchronous Signal » Allows the Extraction and Injection of Synchronous Tributaries 6701 6701 'URS $GG 39 .

Synchronous Digital Hierarchy (SDH) • SDH equipments : Digital Cross Connect » Input: Many STM-N Optical Signals » Output: Many STM-N Optical Signals » Allows Routing of STM-N Signals at High Data Rates 670 1 6701 6701 670 1 40 .

Synchronous Digital Hierarchy (SDH) ■ Core or Transport  Very High Bit Rates ■ Local or Access:  DWDM Required  Low Bit Rates  No DWDM Metropolitan Local or Access Core or Transport ■ Metropolitan  Higher Bit Rates  Possible DWDM 41 .

e Star) arrangements : Mesh Point to Point Hub but SDH allows these to be used in a much more comprehensive way. Mesh and Hub (i. 42 .Synchronous Digital Hierarchy (SDH) • Network Topology Traditional networks make use of Point to Point.

Synchronous Digital Hierarchy (SDH) • Network Topology SDH enables the previous arrangements to be combinated with Rings and Chains of ADMs (Add/Drop Multiplexer) : Chain Ring 43 .

Synchronous Digital Hierarchy (SDH) • Network Topology Point to Point » Large Capacity (with DWDM) » Few Links » Example: Intercontinental Submarine Links MUX MUX 44 .

Tree and Star ADM ADM » Differing Capacity » Many Links ADM » Example: Access Networks MUX ADM ADM MUX MUX ADM ADM MUX ADM MUX MUX ADM 45 .Synchronous Digital Hierarchy (SDH) • Network Topology ADM Ring. Bus.

Synchronous Digital Hierarchy (SDH) • Network Topology ADM • Mesh » Many Links » High Capacity ADM » Example: Transport Networks ADM ADM ADM ADM 46 .

» Most Redundant » Most Expensive Channel 1 Channel 2 . . Channel N Backup 1 Backup 2 PROTECT . WORKING . .Synchronous Digital Hierarchy (SDH) ■ Network protection : • 1+1 Protection Each Bidirectional SDH Channel (2 Fibers) has a dedicated backup channel (2 Fibers). . . Backup N 47 . . . . . .

Channel N PROTECT Backup 48 . . » Most Efficient Channel 1 Channel 2 .Synchronous Digital Hierarchy (SDH) ■ Network protection : • 1:N Protection Every Bidirectional SDH Channel (2 Fibers) » Least Redundant shares a dedicated backup channel (2 Fibers). . . . WORKING .

Synchronous Digital Hierarchy (SDH) ■ Network protection : ring protection ADM ADM ADM ADM ADM ADM ADM ADM 49 .

The recommendation give 50 ms (max) to recover a correct signal.Synchronous Digital Hierarchy (SDH) ■ Network protection : During an Automatic Protection Switching. 50 . the network loses traffic (= the operator loses money!!!). That ’s the reason why it ’s very important for an operator to check the correct working of APS. The main parameter is the switch duration.

Synchronous Digital Hierarchy (SDH) • Quality standard » ITU-T G.821 – Error performance of a digital connection operating below the primary rate » ITU-T M.783 – Recommendation for automatic protection switching and standardized pointer movements It Is Important To Know That We Are Compliant With These Standards 51 .826 – Quality parameters. objectives and calculations for bit rates at or above the primary rate » ITU-T G.2100 – Performance limits for system turn-up and maintenance » ITU-T G.

Synchronous Digital Hierarchy (SDH) • Quality parameters » Errored Seconds (ES) – Seconds during which there is at least one error per block or frame » Severely Errored Seconds (SES) – Length of time during which a major alarm (LOS. Etc. AIS.) is recorded or when 30% of the frames received in one second contain errors » Unavailability – Length of time where SONET equipment is not available (beginning after 10 consecutive SES) 52 . LOF.

Synchronous Digital Hierarchy (SDH) • THANK YOU ! 53 .